X-Git-Url: http://git.tdb.fi/?a=blobdiff_plain;ds=sidebyside;f=source%2Flinal%2Fmatrix.h;h=1c831be6b11cf6f4181366017c739c9ba5e4fd30;hb=7de28b9c89ca4554f5c12746f481f5b385529479;hp=83a64f50dd767ff1497804378be48160e8691ed0;hpb=03f70f6ba9622bb2840a14fc50ac72201cc533b5;p=libs%2Fmath.git

diff --git a/source/linal/matrix.h b/source/linal/matrix.h
index 83a64f5..1c831be 100644
--- a/source/linal/matrix.h
+++ b/source/linal/matrix.h
@@ -8,11 +8,14 @@ namespace Msp {
 namespace LinAl {
 
 /**
-A general mathematical matrix.
+A general mathematical matrix with M rows and N columns.
 */
 template<typename T, unsigned M, unsigned N>
 class Matrix
 {
+public:
+	typedef T ElementType;
+
 private:
 	T data[M*N];
 
@@ -25,11 +28,20 @@ public:
 	static Matrix from_columns(const Vector<T, M> *);
 	static Matrix from_rows(const Vector<T, N> *);
 
+	unsigned rows() const { return M; }
+	unsigned columns() const { return N; }
+
 	T &element(unsigned i, unsigned j) { return data[i+M*j]; }
 	const T &element(unsigned i, unsigned j) const { return data[i+M*j]; }
 	T &operator()(unsigned i, unsigned j) { return element(i, j); }
 	const T &operator()(unsigned i, unsigned j) const { return element(i, j); }
 
+	template<unsigned P, unsigned Q>
+	Matrix<T, P, Q> select(const Vector<unsigned, P> &, const Vector<unsigned, Q> &) const;
+
+	template<unsigned P, unsigned Q>
+	Matrix<T, P, Q> block(unsigned, unsigned) const;
+
 	Matrix &operator*=(T);
 	Matrix &operator/=(T);
 	Matrix &operator+=(const Matrix &);
@@ -68,6 +80,7 @@ inline Matrix<T, M, N> Matrix<T, M, N>::from_columns(const Vector<T, M> *v)
 	for(unsigned i=0; i<M; ++i)
 		for(unsigned j=0; j<N; ++j)
 			m(i, j) = v[j][i];
+	return m;
 }
 
 template<typename T, unsigned M, unsigned N>
@@ -77,6 +90,29 @@ inline Matrix<T, M, N> Matrix<T, M, N>::from_rows(const Vector<T, N> *v)
 	for(unsigned i=0; i<M; ++i)
 		for(unsigned j=0; j<N; ++j)
 			m(i, j) = v[i][j];
+	return m;
+}
+
+template<typename T, unsigned M, unsigned N>
+template<unsigned P, unsigned Q>
+inline Matrix<T, P, Q> Matrix<T, M, N>::select(const Vector<unsigned, P> &row_indices, const Vector<unsigned, Q> &col_indices) const
+{
+	Matrix<T, P, Q> r;
+	for(unsigned j=0; j<P; ++j)
+		for(unsigned i=0; i<Q; ++i)
+			r(j, i) = element(row_indices[j], col_indices[i]);
+	return r;
+}
+
+template<typename T, unsigned M, unsigned N>
+template<unsigned P, unsigned Q>
+inline Matrix<T, P, Q> Matrix<T, M, N>::block(unsigned y, unsigned x) const
+{
+	Matrix<T, P, Q> r;
+	for(unsigned j=0; j<P; ++j)
+		for(unsigned i=0; i<Q; ++i)
+			r(j, i) = element(y+j, x+i);
+	return r;
 }
 
 template<typename T, unsigned M, unsigned N>
@@ -189,8 +225,9 @@ inline bool operator==(const Matrix<T, M, N> &a, const Matrix<T, M, N> &b)
 template<typename T, unsigned M, unsigned N>
 inline Matrix<T, M, N> &Matrix<T, M, N>::exchange_rows(unsigned i, unsigned j)
 {
+	using std::swap;
 	for(unsigned k=0; k<N; ++k)
-		std::swap(element(i, k), element(j, k));
+		swap(element(i, k), element(j, k));
 	return *this;
 }